JP7041479B2 - Organic hydrophilic paint composition, hydrophilic film, and aluminum material for heat exchanger - Google Patents

Description

The present invention relates to the surface of various hard materials such as aluminum materials made of aluminum or aluminum alloys, copper materials made of copper or its alloys, steel materials, plastic materials, and ceramic materials such as glass and tiles. The present invention relates to an organic hydrophilic coating composition for forming a hydrophilic film, a hydrophilic film formed by using the organic hydrophilic coating composition, and an aluminum material for a heat exchanger having the hydrophilic film.

Hydrophilic hard materials having a hydrophilic film on the surface of various hard materials such as metal materials, plastic materials, and ceramic materials are used in various fields. For example, a hydrophilic hard material using an aluminum material as a hard material is lightweight and has excellent thermal conductivity and workability. Therefore, as an aluminum material for various heat exchangers such as fin materials and tube materials, buildings, automobiles, etc. It is widely used in applications such as air conditioning equipment used in.

In such a hydrophilic hard material, not only is it excellent in hydrophilicity, but also various and unique functions are required depending on its use. For example, in the case of aluminum materials for heat exchangers, especially in the case of fin materials, the distance between the fins is for the purpose of increasing the heat exchange efficiency of the heat exchanger and for the purpose of promoting the miniaturization of the heat exchanger and the air conditioner. It is made as narrow as possible and a cut called a louver is made in the fin, and for this reason, the moisture in the air condenses on the heat exchange surface such as the fin surface during cooling and the like, and this Condensed condensed water tends to accumulate on the heat exchange surface as water droplets, reducing the heat exchange area and reducing heat exchange efficiency, or forming bridges between fins to increase ventilation resistance, resulting in a heat exchanger. Since it causes a great decrease in the heat exchange efficiency of the fin material, a hydrophilic film is provided on the surface of the fin material using a hydrophilic coating composition to improve the water wettability of the fin material surface and generate water droplets. Attempts have been made to prevent this from forming water droplets due to condensed water for a long period of time, and such fin materials are previously coated with a hydrophilic film before being incorporated into a heat exchanger. It is supplied as a pre-coated fin material to which long-term hydrophilicity is imparted.

Therefore, conventionally, the hydrophilic coating composition for forming such a hydrophilic film on the surface of the aluminum material for a heat exchanger also starts with an inorganic hydrophilic coating composition such as water glass or silica. Polyvinyl alcohol-based resin, polyacrylamide-based resin, polyacrylic acid-based resin, cellulose-based resin, etc. that solve the problems of the inorganic hydrophilic paint composition, that is, the problems of mold wear during molding and unpleasant odor during cooling operation. Organic hydrophilic coating compositions containing the water-soluble hydrophilic resin of the above have been proposed (see Patent Documents 1 to 4). However, in the hydrophilic film formed by using these organic hydrophilic coating compositions, the problem of the hydrophilic film formed by using the above-mentioned inorganic hydrophilic coating composition can be solved. , There is another new problem, that is, the problem of deterioration of water resistance and long-term hydrophilicity.

Further, as a solution to the problem of the hydrophilic film formed by using these organic hydrophilic coating compositions, a nitrate compound having a monovalent or divalent element is added to the polyvinyl alcohol-based resin and the polyethylene glycol-based resin. The organic hydrophilic coating composition has been proposed (Patent Document 5), and has a stain resistance that can secure long-term hydrophilicity and prevent the adhesion of contaminants such as organic acids and organic esters. As a hydrophilic resin such as polyacrylic acid / sulfonic acid-based copolymer, dibutyl hydroxytoluene, carbazide compound, L-ascorbic acid, sodium L-ascorbic acid, L-ascorbic acid stearate ester, erythorbic acid, sodium erythorbic acid, sulfite. An organic hydrophilic coating composition to which a specific compound selected from sodium is added has also been proposed (Patent Document 6).

By the way, recent air-conditioning equipment used in buildings, automobiles, etc. is often used for heating in winter and for cooling in summer, and such air-conditioning equipment for heating and cooling is often used. The environment in which the aluminum material for heat exchangers used in the air conditioner, especially the fin material, is used is completely different between winter and summer. Various pollutants such as house dust, including oily stains caused by oil and oil, oily stains caused by hair conditioners and cosmetics, oily stains such as nicotine and polycyclic aromatic hydrocarbons caused by smoking, etc. On the contrary, during the cooling operation in summer, it becomes an environment in which these pollutants and the like are hard to adhere due to the generation of dew condensation water. Therefore, in the pre-coated fin material, from the viewpoint of maintaining excellent heat exchange efficiency for as long as possible, the hydrophilic film has a heating operation in addition to the above-mentioned performance such as long-term hydrophilicity. It has so-called "self-cleaning performance" that allows the condensate, etc. that once adhered to the hydrophilic film of the fin material to be easily washed away with the condensed water generated on the surface of the fin material during cooling operation. It is desirable to be there.

Therefore, even in the past, an acrylic polymer having a solid content of 15% by weight or more (A: a polymer containing 40 mol% or more of a sulfonic acid group-containing monomer and a carboxyl group-containing monomer) and 40% by weight or more of the solid content have been used. Ammonia, dimethylethanolamine (DMEA), triethanolamine (TEA), dimethyl in an aqueous solution of an acrylic polymer mixture containing an acrylic polymer (B: a polymer containing 65 mol% or more of a carboxyl group-containing monomer). Obtained by adding amines such as amines (DMA) and alkali metal hydroxides such as sodium carboxymethyl cellulose (CMC-Na), ammonium carboxymethyl cellulose (CMC-ammonyl), and hydroxymethyl cellulose (HMC) at predetermined ratios. A heat exchanger fin having a coating composition and a coating film derived from the coating composition has been proposed. According to the coating composition and the heat exchanger fin, even if a contaminant such as oil or fat adheres to the coating composition, It is said that the contaminants can be washed away by the dew condensation water during the cooling operation and the hydrophilicity can be maintained for a long period of time (Patent Document 7).

Japanese Unexamined Patent Publication No. 63-173,632 Japanese Unexamined Patent Publication No. 02-258,874 Japanese Unexamined Patent Publication No. 05-302,042 Japanese Unexamined Patent Publication No. 09-014,889 Japanese Patent No. 3,890,908 Japanese Patent No. 5,319,952 Japanese Unexamined Patent Publication No. 2010-159,379

However, since the polyvinyl alcohol-based resin is used as the resin component in the hydrophilic film formed by using the organic hydrophilic coating composition of Patent Document 5, it exhibits a certain level of performance in initial hydrophilicity and long-term hydrophilicity. However, the hydroxyl groups in the two linear polymer chains adjacent to each other of the polyvinyl alcohol-based resin gradually form hydrogen bonds to promote the crystallization of the so-called polyvinyl alcohol-based resin, and the number of hydroxyl groups in the polyvinyl alcohol-based resin gradually decreases. However, it is not always sufficient for long-term hydrophilicity to form a hydrophilic film of an aluminum material for heat exchange of air-conditioning equipment for heating and cooling, especially a fin material, which is used throughout the year.

Further, in the hydrophilic film formed by using the organic hydrophilic coating composition of Patent Document 6, the description of the examples shows that the resin components (paint numbers 1 to 1) forming the hydrophilic resin layer (B) are formed. For 19 and 25 to 27), paint numbers 1 to 16 and 25 to 27 are polyacrylic acid / sulfonic acid-based copolymers, and paint number 17 is a combination of polyacrylic acid, polyacrylamide, and polyethylene glycol. Numbers 18 and 19 are combinations of polyacrylamide, polyethylene glycol, and PVA, and only very limited resin components have been confirmed, and all of the resin components forming the hydrophilic resin layer (B) have been confirmed. Acrylic resin is used. Then, the present inventors conducted a follow-up experiment using the resin components forming the hydrophilic resin layers (B) of the paint numbers 2, 17, and 18, and found that all of them had initial hydrophilicity, water resistance, and adhesion. It was confirmed that although it exhibits predetermined performance in terms of sex, it does not exhibit the desired performance in terms of long-term hydrophilicity and self-cleaning performance. According to the studies by the present inventors, this long-term hydrophilicity and self-cleaning performance, particularly self-cleaning performance, is not exhibited because the main component of the resin component forming the hydrophilic resin layer (B) is polyacrylic acid or polyacrylamide. It was found that this acrylic resin is not suitable for aluminum materials for heat exchangers, especially fin materials, because it is considered to be caused by a marked shortage of the hydroxyl value in the coating composition.

Further, the coating composition of Patent Document 7 contains a special mixture of acrylic polymers (A) and (B) as main components, and also uses a special alkali metal hydroxide and ammonia. Alternatively, the addition of amine is indispensable, and the product cost must be high. In addition, the generation of amine odor is unavoidable during painting work, and there is concern about the generation of amine odor during heating and cooling operation. There is a problem of mold wear during molding in the sex-based paint composition and another unpleasant odor different from the unpleasant odor during cooling operation.

Therefore, the present inventors have no problem of generating an unpleasant odor in addition to the performance such as long-term hydrophilicity so far, and can easily wash away the contaminants and the like once adhering to the surface of the hydrophilic film during use. As a result of diligent studies on the development of an organic hydrophilic coating composition that can exhibit possible self-cleaning performance and is useful for applications of aluminum materials for heat exchangers such as pre-coated fin materials, it is surprising. In particular, by using a polyvinyl alcohol-based resin as a resin component and adding ascorbic acid as an additive component at a predetermined ratio, ascorbic acid exerts a hydrogen bond suppressing effect and crystallizes the polyvinyl alcohol-based resin. The present invention has been completed by finding that it is remarkably suppressed, exhibits long-term hydrophilicity, and exhibits self-cleaning performance.

Therefore, an object of the present invention is to form an organic film having self-cleaning performance in addition to long-term hydrophilicity on the surface of various hard materials such as metal materials, plastic materials, and ceramic materials. To provide a hydrophilic coating composition.
Another object of the present invention is to provide an aluminum material for a heat exchanger such as a precoated fin material having a hydrophilic film formed by such an organic hydrophilic coating composition.

That is, the gist of the present invention is as follows.
(1) As a resin component , a polyvinyl alcohol-based resin having a saponification degree of 97 mol% or more and an average degree of polymerization (n) of 1000 to 1700 is contained at a ratio of 40 to 100 g / L, and a polyethylene glycol-based resin is contained in an amount of 4 to 15 g / L. An organic hydrophilic coating composition containing ascorbic acid at a ratio of 0.02 to 39 g / L as an additive component and having a hydroxyl value of 550 to 1300 mgKOH / g as a solid component .
(2) The organic hydrophilic coating composition according to (1) above, wherein the polyvinyl alcohol-based resin is a completely saponified type having a saponification degree of 98.5 mol% or more and 99.8 mol% or less .
(3) A film obtained by applying and baking the organic hydrophilic coating composition according to (1) or (2) above, the hydrophilicity characterized by covering a part or all of the surface of the main body of a hard material. Film.
(4) Having a hydrophilic film obtained by applying and baking the organic hydrophilic coating composition according to (1) or (2) above on a part or all of the surface of an aluminum material made of aluminum or an aluminum alloy. A featured aluminum material for heat exchangers.
(5) The aluminum material for heat exchanger according to (4) above, wherein the aluminum material for heat exchanger is a pre-coated fin material.

According to the organic hydrophilic coating composition of the present invention, there is no problem of generating an unpleasant odor on the surface of various hard materials such as metal materials, plastic materials, ceramic materials, etc., and the performance such as long-term hydrophilicity is improved. In addition, it is possible to form a hydrophilic film having self-cleaning performance.

Further, the aluminum material for a heat exchanger such as a pre-coated fin material having a hydrophilic film formed by using the organic hydrophilic coating composition of the present invention does not have a problem of generating an unpleasant odor and has performance such as long-term hydrophilicity. In addition, even if the surface is contaminated during heating, etc., where dew condensation water does not occur, the self-cleaning performance that water such as dew condensation water is easily washed away by the approaching water during cooling, etc. is demonstrated. In addition, the cleaning work that is performed regularly becomes extremely easy as compared with the conventional case.

Hereinafter, the organic hydrophilic coating composition of the present invention, the hydrophilic film, and the aluminum material for heat exchanger will be described in detail.
The organic hydrophilic coating composition of the present invention contains a polyvinyl alcohol-based resin (PVA) as a resin component and ascorbic acid as an additive component.

In the organic hydrophilic coating composition of the present invention, the polyvinyl alcohol-based resin (PVA) constituting the resin component is a linear polymer having a repeating structure of − [CH ₂ -CH (OH)] _n −. A completely saponified type polyvinyl alcohol having a saponification degree of 97 mol% or more, more preferably 98.5 mol% or more and 99.8 mol% or less is preferable, and an average degree of polymerization (n) thereof is preferable. It is preferably 500 to 2000, more preferably 1000 to 1700 PVA. If the saponification degree is lower than 97 mol%, both hydrophilicity and water resistance may deteriorate, and if the average degree of polymerization (n) is lower than 500, both hydrophilicity and water resistance may deteriorate. On the contrary, if it is higher than 2500, the viscosity may increase and the workability may decrease.

Such polyvinyl alcohol-based resin (PVA) includes modified products into which various functional groups have been introduced. For example, the product name WO-320N manufactured by Nippon Synthetic Chemical Co., Ltd., which has an ethylene oxide group introduced therein, has a carboxyl group. In addition to these, many products such as those with acetoacetyl groups and sulfonic acid groups have been put on the market, including the product name T-330H manufactured by Nippon Synthetic Chemical Co., Ltd. Can be used.

Further, with respect to the resin component of the above-mentioned organic hydrophilic coating composition, in order to further improve the long-term hydrophilicity of the obtained hydrophilic film, it is preferable to add a polyethylene glycol-based resin (PEG). The weight average molecular weight of such polyethylene glycol-based resin (PEG) is preferably 1000 or more and 20000 or less, more preferably 4000 or more and 11000 or less, and the copolymer of polyethylene glycol or ethylene glycol / propylene. A copolymer such as glycol can be exemplified. If the weight average molecular weight is less than 1000, the hydrophilicity may be relatively lowered, and if it is larger than 20000, the stability of the paint bath may be impaired. When PEG is blended in the resin component, the blending ratio of this PEG is preferably 10% by mass or more and 22% by mass or less, preferably 14% by mass or more and 19% by mass or less with respect to the total of PVA and PEG. If the blending ratio of PEG is lower than 10% by mass, the effect of blending PEG is poor, and conversely, even if it is added in excess of 22% by mass, the effect of blending PEG is lowered.

Then, in the present invention, the above-mentioned polyvinyl alcohol-based resin (PVA) is used as a resin component, and ascorbic acid having a hydrogen bond suppressing effect is added to these resin components as an additive component. Ascorbic acid used as an additive component has two hydroxyl groups bonded to a five-membered ring, thereby forming a hydrophilic film. In PVA, which is a linear polymer, ascorbic acid is a linear polymer chain of PVA. Intervenes between the two, expands a part between each linear polymer chain, suppresses hydrogen bonding of hydroxyl groups (OH) in each expanded linear polymer chain, and has a so-called hydrogen bond suppressing effect. It is considered that it suppresses the decrease of the expressed free hydroxyl group and prevents the hydrophilicity of the hydrophilic film from decreasing for a long period of time.

Further, as ascorbic acid to be added as an additive component, there are stereoisomers of L-ascorbic acid and erythorbic acid, both of which are included in the scope of the present invention.

In the present invention, the mixing ratio of the polyvinyl alcohol-based resin (PVA) used as a resin component and ascorbic acid used as an additive component is usually 40 g / L or more and 100 g / L or less, preferably 50 g / L for PVA. The ratio of ascorbic acid as an additive component is 0.02 g / L or more and 39 g / L or less, preferably 0.04 g / L or more and 17 g / L or less. Here, if the compounding ratio of PVA is lower than 40 g / L, it may be difficult to obtain the required film thickness by painting, and conversely, if it is higher than 100 g / L, the stability of the paint may be lowered. If the blending ratio of ascorbic acid, which is an additive component, is lower than 0.02 g / L, stable hydrophilicity may not be obtained, and conversely, if it exceeds 39 g / L, self-cleaning performance / There is a risk that the problem of poor appearance will occur. When polyethylene glycol-based resin (PEG) is used as the resin component, it is usually 4 g / L or more and 15 g / L or less, preferably 9 g / L or more and 14 g / L or less in consideration of the mixing ratio with PVA. Often, if it is lower than 4 g / L, the hydrophilicity improving effect may be lowered, and conversely, if it is higher than 15 g / L, the stability of the paint may be lowered.

In the present invention, the hydroxyl value of the organic hydrophilic coating composition is preferably 550 mgKOH / g or more and 1300 mgKOH / g or less, and more preferably 700 mgKOH / g or more and 1150 mgKOH / g or less. When the hydroxyl value falls within the above range, good hydrophilicity can be obtained over a long period of time. Here, as the acrylic resin as used in Patent Document 6, for example, the product name UH-2000 manufactured by Toagosei Co., Ltd. is about 20 mgKOH / g, and the product name Hitaroid 6500 manufactured by Hitachi Kasei Co., Ltd. is 30 mgKOH. Its hydroxyl value is extremely low, such as about / g, and it is not suitable as a resin component used in the organic hydrophilic coating composition of the present invention.

The organic hydrophilic coating composition of the present invention contains the above-mentioned polyvinyl alcohol-based resin (PVA) as a resin component and the above-mentioned ascorbic acid as an additive component, and if necessary, for the purpose of preventing spoilage during storage. Antiseptic agents with antibacterial and anti-mold effects such as organic copper, organic iodine, imidazole, isothiazoline, pyrithione, triazine, silver, and rust preventives such as tannic acid, galvanic acid, fuitic acid, and phosphinic acid. Agents, leveling agents such as alkyl esters of polyalcohol and polyethylene oxide condensates, fillers such as polyacrylamide and polyvinylacetamide added within a range that does not impair compatibility, and colorants such as titanium oxide and phthalocyanine compounds. Alternatively, a third additive component such as an alkyl sulfate ester salt or a surfactant such as an alkyl sulfosuccinate system can be added.

In preparing the organic hydrophilic coating composition of the present invention, the above-mentioned resin component, additive component, and third additive component may be water, acetone, ethylene glycol monobutyl ether (also known as "butyl cellosolve" or "buty cello") or the like. It is prepared by dissolving or dispersing in a suitable dispersion medium, preferably an aqueous dispersion medium such as water, isopropyl alcohol, or ethanol. The preparation method at this time is not particularly limited, but for example, since polyvinyl alcohol-based resin (PVA) is relatively difficult to dissolve in water, it is preferable to first disperse PVA in water at room temperature for 5 to 10 minutes. After that, it is heated at 80 to 90 ° C. for 30 to 60 minutes to dissolve it, and then water is added to a predetermined concentration, and then, if necessary, a polyethylene glycol-based resin (PEG) is added and dissolved under stirring. After that, ascorbic acid is added as a uniform aqueous solution and mixed.

The method of applying the organic hydrophilic coating composition of the present invention to the surface of various hard materials is also not particularly limited. For example, a method using a commonly used roll coater or a gravure convenient for controlling the coating amount. It is possible to adopt a method using a roll, a natural coating method that is convenient for thick coating, a reverse coating method that is advantageous for finishing the coated surface beautifully, and the like.

For example, when preparing an aluminum material for a heat exchanger such as the precoated fin material of the present invention using the organic hydrophilic coating composition of the present invention, when forming a hydrophilic film on the surface of the aluminum material, first, a roll is used. The coating composition is applied to the surface of the aluminum material using a coater or the like, and then heated by a floater oven or the like under high temperature ventilation, preferably 10 to 30 m / min at a high temperature of 200 to 300 ° C. Heat for ~ 15 seconds.

The film thickness of the hydrophilic film formed on the surface of the hard material using the organic hydrophilic coating composition of the present invention varies depending on the type and application of the hard material, and is not particularly limited. For example, a precoated fin material may be used. In some cases, it is usually 0.05 to 5 μm, preferably 0.1 to 2 μm, and more preferably about 0.5 to 1.5 μm. The ratio of the three main components contained in the hydrophilic film obtained in the present invention is polyvinyl alcohol resin (PVA): 42.6% by weight to 96.1% by weight, polyethylene glycol resin (PEG) :. 0.0% by weight to 27.3% by weight, and ascorbic acid: 0.017% by weight to 47.0% by weight.

Here, according to the study by the present inventors, in the organic hydrophilic coating composition of the present invention, ascorbic acid having the above-mentioned hydrogen bond suppressing effect has two hydroxyl groups bonded to the five-membered ring in the molecule. The size of the molecule of ascorbic acid that shows affinity with the hydroxyl groups in the two linear polymer chains adjacent to each other of the polyvinyl alcohol-based resin (PVA) in the resin component and penetrates between these two linear polymer chains. Correspondingly, it spreads between the two linear polymer chains, exerts a hydrogen bond inhibitory effect and suppresses the crystallization of PVA, and allows relatively small molecules such as water molecules to approach each other. It is considered that it exhibits good hydrophilicity for a long period of time, and at the same time, it blocks the approach of relatively large molecules such as oily stains and pollutants such as house dust and exhibits good stain resistance. .. In this way, it exhibits good hydrophilicity over a long period of time, and at the same time, it blocks the approach of relatively large contaminants and exhibits good stain resistance. Therefore, for example, as a hydrophilic film of a precoated fin material. When used, even if pollutants such as oily stains and house dust adhere to the surface of the hydrophilic film during heating when dew condensation water does not occur, the degree of adhesion is not strong and cooling is performed. When water such as dew condensation water approaches at times, this water easily enters between the hydrophilic film and the pollutant, and the pollutant rises from the surface of the hydrophilic film, and is washed away with water such as dew condensation water for self-cleaning. It is considered to demonstrate its performance.

Hereinafter, preferred embodiments of the present invention will be specifically described based on Examples and Comparative Examples.
In the following Examples and Comparative Examples, the hydrophilicity (initial hydrophilicity and long-term hydrophilicity), water resistance, adhesion, and self-cleaning performance were determined by the following methods, respectively.

[Preparation of test pieces]
Examples 1 to 4, 6 to 9, 11, 12, 14 and Comparative Examples 1, 2, and 4 to the aluminum material (AA3102; thickness 0.10 mm) that had been degreased and washed by a conventional method. In No. 7, a corrosion-resistant film was formed on the surface by the following chromate treatment, and in Examples 5, 10, 13 and Comparative Example 3, a surface treatment was performed to form a corrosion-resistant coating film on the surface by the following urethane primer treatment. , A surface-treated aluminum piece for preparing a test piece was prepared by cutting it into a size of 7 cm × 15 cm.
(1) Chromate treatment: A chromate treatment agent (trade name: Alsurf 407/47 manufactured by Nippon Paint Co., Ltd.) was used to form a corrosion-resistant film of Cr: 100 mg / m ² on the surface of the aluminum material.
(2) Urethane primer treatment: A primer treatment agent (trade name: Superflex SF150 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) is applied to the surface of the aluminum material and cured at 270 ° C for 10 seconds to achieve a film thickness of 0.6 g / m ² . A corrosion resistant coating film was formed.

The organic hydrophilic coating composition of each example and comparative example was applied to the surface of the obtained surface-treated aluminum piece using a bar coater, and baked under the condition of 230 ° C. for 10 seconds to obtain the surface of the surface-treated aluminum piece. A hydrophilic film of 0.6 to 0.7 g / m ² was formed on the surface, and test pieces of each Example and Comparative Example were prepared.

[Evaluation of hydrophilicity (initial hydrophilicity and long-term hydrophilicity)]
Press oil (trade name: AF-2C manufactured by Idemitsu Kosan Co., Ltd.) was applied to the test pieces of each Example and Comparative Example prepared in this manner, heated and dried under drying conditions of 160 ° C. for 10 minutes, and immediately after drying. The initial hydrophilicity of the product and the long-term hydrophilicity after immersion in RO water purified with a reverse osmosis (RO) membrane at room temperature, under running water, and under immersion conditions of 500 hours were measured.
To measure the initial hydrophilicity and long-term hydrophilicity at this time, 2 μL of pure water was dropped onto the hydrophilic film of the test piece placed horizontally, and the contact angle of the formed water droplet was measured by a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.). : CA-A), and the evaluation of hydrophilicity is as follows: Evaluation point 5: Contact angle ≤ 10 °, Evaluation point 4: Contact angle 11 to 20 °, Evaluation point 3: 21 to 30 °, Evaluation point 2 : The evaluation criteria were 31 to 35 ° and evaluation score 1: ≧ 36 °, and the case where the evaluation score ≧ 2 was considered to be hydrophilic (passed).

[Evaluation of water resistance]
The test pieces of each example and comparative example were immersed in RO water at room temperature for 240 hours under running water conditions, and the coating film on the surface of the test piece after immersion was visually observed to check the coating film for abnormalities such as blisters. In addition, the presence or absence of peeling is checked in the grid tape test (former JIS K 5400), and if neither abnormality in these visual observations nor peeling in the tape peeling test is observed, the result is passed, and the abnormality in visual observation is also confirmed. And, if any of the peeling in the tape peeling test was observed, it was rejected.

[Evaluation of adhesion]
For the test pieces of each example and comparative example, make 100 1 mm square squares on the coated surface with a cutter knife according to the grid tape test (formerly JIS K 5400), and then attach adhesive tape to this surface. After abrupt peeling, the presence or absence of peeling of the squares was examined, and if no peeling was observed, it was judged as pass, and if it was found, it was rejected.

[Evaluation of self-cleaning]
For the test pieces of each Example and Comparative Example, a commercially available oil-based marker (trade name: Twin Marker MFN-15FB-B manufactured by Pilot) was used, and the surface of the hydrophilic film of the test piece was the lower half of the surface. In the area of, a square mark (area 225 mm ² ) having a width of 15 mm and a length of 15 mm was marked to make it an oily stain.
Next, the test piece with the oily stain was set against the wall so that the inclination angle with respect to the horizontal plane was 90 °, and a sprayer was used to spray the upper half area of the set test piece with a sprayer. The spray was repeated 150 times at (amount of one spray: 0.8 to 0.9 ml), and the ratio (removal rate) of the water sprayed on the upper half region flowing to the lower half region to wash away oily stains was examined. When spraying water with this spraying device, the sprayed water was prevented from directly coming into contact with oily stains.

Regarding the removal rate of oily stains, after the spraying of water is completed, the flow from the upper half to the lower half of the water is completed, and after waiting for the surface of the test piece to dry, the area where the oily stains are washed away (washed area). : Mm ² ) was measured, and the ratio of the washed-out area (mm ² ) to the total area of oily stains (225 mm ² ) was taken as the removal rate (%).
Regarding the evaluation of this self-cleaning property, evaluation point 5: removal rate> 81%, evaluation point 4: removal rate 61 to 80%, evaluation point 3: removal rate 41 to 60%, evaluation point 2: removal rate 20 to The evaluation criteria were 40% and evaluation point 1: removal rate <20%, and when the evaluation point ≥ 2, it was evaluated as self-cleaning (passed).

〔Comprehensive evaluation〕
Regarding the comprehensive evaluation of the organic hydrophilic coating composition obtained in each Example and Comparative Example, all the evaluation items of initial hydrophilicity and long-term hydrophilicity regarding hydrophilicity, water resistance, adhesion, and self-cleaning were passed. Evaluate by taking into account the total of the evaluation points of initial hydrophilicity, long-term hydrophilicity, and self-cleaning regarding whether or not there is hydrophilicity. ◎: All evaluation items pass and the total evaluation points are 13 or more. In the case of ◯: all evaluation items passed and the total evaluation score was 9 to 12, and ×: evaluation was performed based on the case where any of the evaluation items failed.

[Examples 1 to 14 and Comparative Examples 1 to 4]
As the polyvinyl alcohol-based resin (PVA) as a resin component, [PVA-1]: polyvinyl alcohol having a saponification degree of 99.3% and an average degree of polymerization of 1,000 (trade name: VC-10 manufactured by Nippon Vinegar Vipovar), [PVA -2]: Polyvinyl alcohol with a saponification degree of 98.0% and an average degree of polymerization of 1.700 (trade name: JF-17L manufactured by Nippon Vinegar Vipovar), and [PVA-3]: a sacrifice degree of 97.0% and an average degree of polymerization. Polyethylene glycol with a degree of 1700 (trade name: VM-17 manufactured by Nippon Vinegar Vipovar) is used, and as a polyethylene glycol-based resin (PEG) as a resin component, [PEG-1]: polyethylene glycol having a number average molecular weight of 6000 (Sanyo). Kasei Kogyo Co., Ltd. trade name: PEG-6000S), [PEG-2]: polyethylene glycol having a number average molecular weight of 1500 (Sanyo Kasei Kogyo Co., Ltd. trade name: PEG-1500), and [PEG-3]. ]: Polyethylene glycol having a number average molecular weight of 13000 (trade name: PEG-13000 manufactured by Sanyo Kasei Kogyo Co., Ltd.) was used. As the ascorbic acid as an additive component, vitamin C (L-ascorbic acid) [food additive grade] manufactured by Fuso Chemical Industry Co., Ltd. was used.

First, for the polyvinyl alcohol-based resin (PVA) as the resin component, a PVA dispersion having a PVA concentration of 120 g / L was prepared using water as a dispersion medium, and the polyethylene glycol-based resin (PEG) as the resin component was prepared. Using water as a dispersion medium, a PEG dispersion having a PEG concentration of 100 g / L was prepared.
Next, as the ascorbic acid as an additive component, water was used as a solvent, and an ascorbic acid aqueous solution having an ascorbic acid concentration of 10 g / L was prepared and used.
Further, using the PVA dispersion, the PEG dispersion, and the ascorbic acid aqueous solution prepared as described above, the organic hydrophilic coating compositions of Examples and Comparative Examples having the compositions shown in Table 1 were prepared.

[Comparative Examples 5 to 7]
[PAAc]: Polyacrylic acid (BASF: Joncryl1532) is used as the resin component polyacrylic acid resin (PAAc), and [PAAm]: Polyacrylamide (Arakawa) is used as the resin component polyacrylamide resin (PAAm). Chemical Industry Co., Ltd .: Polymasset 512) was used, and [SAcP]: acrylic acid-sulfonic acid based copolymer (manufactured by Toa Synthetic Co., Ltd .: Aron A-12SL) was used as the sulfonic acid-based resin (SAcP) of the resin component. In addition, [SAA]: a surfactant (manufactured by Nichiyu Co., Ltd .: Rapisol A-90) was used.

First, for the polyacrylic acid-based resin (PAAc) as the resin component, water is used as a dispersion medium to prepare a PAAc dispersion having a PAAc concentration of 200 g / L, and the polyacrylamide-based resin (PAAm) as the resin component is prepared. A PAAm dispersion having a PAAm concentration of 100 g / L was prepared using water as a dispersion medium, and water was used as a dispersion medium for the sulfonic acid-based resin (SAcP) of the above resin component, and SAcP having a SAcP concentration of 100 g / L was used. The dispersion was adjusted.
Next, the PAAc dispersion, PAAm dispersion, SAcP dispersion, PVA dispersion, and PEG dispersion prepared as described above, and the above-mentioned surfactant and ascorbic acid aqueous solution are used to have the composition shown in Table 1. The organic hydrophilic paint composition of each comparative example was prepared.

For the organic hydrophilic coating compositions of Examples and Comparative Examples prepared in this way, in order to measure the hydroxyl value, a composition consisting of each component excluding the dispersion medium (water) was prepared, and JIS According to the neutralization titration method described in K0070-1992, an acetylating reagent is added to the sample, heated in a glycerin bath, cooled, then a phenolphthalein solution is added as an indicator, and the sample is titrated with a potassium hydroxide ethanol solution. The hydroxyl group was measured.
The results are shown in Table 1.

For the organic hydrophilic coating compositions of each Example and Comparative Example, test pieces of each Example and Comparative Example are prepared according to the above method, and hydrophilicity (initial hydrophilicity and long-term hydrophilicity), according to the above method. Water resistance, adhesion, and self-cleaning performance were evaluated.
The results are shown in Table 1.

Claims (5)

As a resin component, a polyvinyl alcohol-based resin having a saponification degree of 97 mol% or more and an average degree of polymerization (n) of 1000 to 1700 is contained at a ratio of 40 to 100 g / L, and a polyethylene glycol-based resin is contained in the range of 4 to 15 g / L. An organic hydrophilic coating composition containing ascorbic acid as an additive component at a ratio of 0.02 to 39 g / L and having a hydroxyl value of 550 to 1300 mgKOH / g as a solid component . The organic hydrophilic coating composition according to claim 1 , wherein the polyvinyl alcohol-based resin is a completely saponified type having a saponification degree of 98.5 mol% or more and 99.8 mol% or less . A film obtained by applying and baking the organic hydrophilic coating composition according to claim 1 or 2 , characterized in that it covers a part or all of the surface of a hard material. A heat exchange characterized by having a hydrophilic film obtained by applying and baking the organic hydrophilic coating composition according to claim 1 or 2 on a part or all of the surface of an aluminum material made of aluminum or an aluminum alloy. Dexterous aluminum material. The aluminum material for heat exchanger according to claim 4 , wherein the aluminum material for heat exchanger is a precoated fin material.